Vertical transport mechanisms of black carbon over East Asia in spring during the A‐FORCE aircraft campaign

Oshima, Naga; Koike, M.; Kondo, Yutaka; Nakamura, Hisashi; Moteki, Nobuhiro; Matsui, Hitoshi; Takegawa, N.; Kita, K.

doi:10.1002/2013jd020262

Cited by 34 publications

(61 citation statements)

References 98 publications

(170 reference statements)

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“…The model generally overestimates BC at 40-45 • N. Another major bias is that there is an overestimate in model simulations at lower altitudes and an underestimate at higher altitudes near 50 • N, mainly because there are large uncertainties in the calculations of vertical transport of BC (Koffi et al, 2012;Oshima et al, 2013). Oshima et al (2013) identified that the uplifting of BC in association with migratory cyclones over northeastern China and the subsequent BC transport by the midlatitude westerlies provided the major pathway for BC export from EA to the free troposphere over the western Pacific during the springtime A-FORCE period. Here the observed high BC concentrations aloft in April may be caused by the same mechanism.…”

Section: -35mentioning

confidence: 98%

“…Here we use the GEOS-Chem model (version 9-01-03) with a horizontal resolution of 2 • latitude by 2.5 • longitude and 47 vertical layers to simulate BC concentrations for March and April 2010, following six months of spin-up. BC simulations in GEOS-Chem have been evaluated over the United States using surface measurements from the Interagency Monitoring of Protected Visual Environments (IM-PROVE) network (Park et al, 2003) and over the Himalayas and the Tibetan Plateau using wet deposition flux measurements (Kopacz et al, 2011). The simulation of BC in GEOSChem has been discussed by Park et al (2003) and Park et al (2005); here we describe the key features of the BC simulation, as they pertain to this study.…”

Section: Geos-chem Model and Its Adjointmentioning

confidence: 99%

“…Dry deposition is implemented following a standard resistance-in-series scheme as described by Wang et al (1998). Dry deposition is not important for fine aerosols (Park et al, 2005) and is small compared to wet deposition in BC simulation (Park et al, 2003). In GEOSChem, the global annual mean dry deposition velocity for BC is 0.1 cm s −1 , which is typical of current models (Wang et al, 2011).…”

Section: Geos-chem Model and Its Adjointmentioning

confidence: 99%

“…Many models treat BC aging as an exponential decay process with a fixed e-folding time in the range of 1-2 d (Chung and Seinfeld, 2002;Cooke et al, 2002;Liu et al, 2009b;Park et al, 2003). However, large uncertainties remain and a number of studies have indicated a faster aging rate (Croft et al, 2005;Riemer et al, 2004Riemer et al, , 2010.…”

Section: Idealized Transpacific Bc Transport Modelmentioning

confidence: 99%

“…Previous studies solved the inverse problem using methods suitable for adjusting a few emissions scaling factors over broad regions (Fu et al, 2012;Park et al, 2003;. The adjoint method developed in recent studies overcomes this difficulty by enabling grid-scale refinement of emissions factors (Hakami et al, 2005).…”

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confidence: 99%

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Analysis of transpacific transport of black carbon during HIPPO-3: implications for black carbon aging

et al. 2014

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Abstract. Long-range transport of black carbon (BC) is a growing concern as a result of the efficiency of BC in warming the climate and its adverse impact on human health. We study transpacific transport of BC during HIPPO-3 using a combination of inverse modeling and sensitivity analysis. We use the GEOS-Chem chemical transport model and its adjoint to constrain Asian BC emissions and estimate the source of BC over the North Pacific. We find that different sources of BC dominate the transport to the North Pacific during the southbound (29 March 2010) and northbound (13 April 2010) measurements in HIPPO-3. While biomass burning in Southeast Asia (SE) contributes about 60 % of BC in March, more than 90 % of BC comes from fossil fuel and biofuel combustion in East Asia (EA) during the April mission. GEOS-Chem simulations generally resolve the spatial and temporal variation of BC concentrations over the North Pacific, but are unable to reproduce the low and high tails of the observed BC distribution. We find that the optimized BC emissions derived from inverse modeling fail to improve model simulations significantly. This failure indicates that uncertainties in BC removal as well as transport, rather than in emissions, account for the major biases in GEOS-Chem simulations of BC over the North Pacific.The aging process, transforming BC from hydrophobic into hydrophilic form, is one of the key factors controlling wet scavenging and remote concentrations of BC. Sensitivity tests on BC aging (ignoring uncertainties of other factors controlling BC long range transport) suggest that in order to fit HIPPO-3 observations, the aging timescale of anthropogenic BC from EA may be several hours (faster than assumed in most global models), while the aging process of biomass burning BC from SE may occur much slower, with a timescale of a few days. To evaluate the effects of BC aging and wet deposition on transpacific transport of BC, we develop an idealized model of BC transport. We find that the mid-latitude air masses sampled during HIPPO-3 may have experienced a series of precipitation events, particularly near the EA and SE source region. Transpacific transport of BC is sensitive to BC aging when the aging rate is fast; this sensitivity peaks when the aging timescale is in the range of 1-1.5 d. Our findings indicate that BC aging close to the source must be simulated accurately at a process level in order to simulate better the global abundance and climate forcing of BC.

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Section: -35mentioning

confidence: 98%

Section: Geos-chem Model and Its Adjointmentioning

confidence: 99%

Section: Geos-chem Model and Its Adjointmentioning

confidence: 99%

Section: Idealized Transpacific Bc Transport Modelmentioning

confidence: 99%

mentioning

confidence: 99%

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Analysis of transpacific transport of black carbon during HIPPO-3: implications for black carbon aging

et al. 2014

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Variability of aerosol particle number concentrations observed over the western Pacific in the spring of 2009

Takegawa

Moteki

Oshima³

et al. 2014

JGR Atmospheres

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Airborne measurements of aerosols were conducted over the western Pacific in the spring of 2009 during the Aerosol Radiative Forcing in East Asia (A-FORCE) aircraft campaign. The A-FORCE flights intensively covered an important vertical-latitudinal range in the outflow region of East Asia (0-9 km altitude; 27°N-38°N). This paper presents the variability of aerosol particle number concentrations obtained by condensation particle counters and a Single-Particle Soot Photometer (SP2), with the focus on those in the free troposphere. The number concentration data include total condensation nuclei with particle diameters (d p ) larger than 10 nm (total CN 10 ), PM 0.17 -CN 10 (d p~1 0-130 nm), and SP2 black carbon (N BC ; d p~7 5-850 nm). Large increases in total CN 10 that were not associated with N BC were observed in the free troposphere, suggesting influences from new particle formation (NPF). Statistical characteristics of total CN 10 , PM 0.17 -CN 10 , and N BC in the lower troposphere (LT; 0-3 km), middle troposphere (MT; 3-6 km), and upper troposphere (UT; 6-9 km) are investigated. The correlation between total CN 10 and N BC , along with the ratio of PM 0.17 to total CN 10 and carbon monoxide mixing ratio (CO), is used to interpret the observed variability. The median concentrations of total CN 10 and PM 0.17 -CN 10 in the UT were higher than those in the MT by a factor of~1.4 and 1.6, respectively. We attribute the enhancements of CN 10 in the UT to NPF. Possible mechanisms affecting NPF in the free troposphere are discussed.

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Wet deposition of black carbon at a remote site in the East China Sea

et al. 2014

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Mass concentrations of black carbon (BC) in air (M BC ) and rainwater (C BC ) in the East China Sea were measured at Hedo on Okinawa Island, Japan, from April 2010 to March 2013. The monthly averaged M BC and C BC showed marked seasonal variations, being highest in spring (0.32 ± 0.13 μg m À3 and 92 ± 76 μg L À1 , respectively) and lowest in summer (0.06 ± 0.03 μg m À3 and 8.0 ± 4.1 μg L À1 , respectively). The high M BC and C BC in spring were associated with transport of air masses from the Asian continent by northwesterly winds. The BC wet deposition flux (F BC ), estimated as the product of C BC and precipitation amount, also showed a distinct seasonal variation. The monthly average F BC during the four spring seasons (16.8 ± 6.7 mg m À2 month À1 ) was about 3 times higher than the annual average F BC (5.5 ± 9.9 mg m À2 month À1 ) owing to the high C BC and precipitation amount in spring. As a result, about 76% of the annual BC deposition occurred in spring on average. The F BC in spring is comparable to the average BC net flux in North China, indicating the importance of precipitation over the East China Sea as a sink of BC transported from North China. In summer, C BC values were correlated with M BC for rain events associated with local convective activity, as identified by the convective available potential energy. A one-dimensional thermodynamic model successfully explained the relation between C BC and M BC .

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Vertical transport mechanisms of black carbon over East Asia in spring during the A‐FORCE aircraft campaign

Cited by 34 publications

References 98 publications

Analysis of transpacific transport of black carbon during HIPPO-3: implications for black carbon aging

Analysis of transpacific transport of black carbon during HIPPO-3: implications for black carbon aging

Variability of aerosol particle number concentrations observed over the western Pacific in the spring of 2009

Wet deposition of black carbon at a remote site in the East China Sea

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